It's a copper underwing, Amphipyra Pyramidea. It took me a bit of time as there is a very close relative called aSvensson's Copper Underwing, Amphipyra Berbera which is still common so it was very hard to tell!

Thank you, how could you tell it was the copper underwing not the Svenssons Copper underwing? We were pretty sure it was a copper underwing but didn't know how to tell the two copper underwing species apart.

I know I don't know either because the only way tell the difference between the two is by dissecting them and I wouldn't do that personally but I thought you just wanted to know what fairly exact species it was